Method of applying bitumen to a concrete foundation



Patented Apr. 3, 1934 METHOD OF APPLYING BITUMEN TO A CONCRETE FOUNDATION Leonard Gowen Gabriel and John Frederick Blctt, London, England, assignors, by mesne assignments, to Colas Roads, Inn, Boston, Mass a corporation of Massachusetts No Drawing. Application August 10, 1929, Serial No. 385,069. In Great Britain September 13,

.8 Claims.

This invention relates to methods of applying bitumen to a concrete foundation and is particularly concerned with the making and repair of concrete roads.

5 One object of this invention is to provide a road which shall combine the advantages of a concrete foundation with those of a bituminous :surface. The direct application of bitumen (either applied in a hot liquid state or by means of 110 a cold aqueous emulsion) to an existing concrete road does not produce a bituminous coating with sufficient adhesion to the concrete to prevent scaling or picking up of the bitumen under trafiic, nor does it impart to the road any ap- 15 preciable degree of resilience.

This invention provides a method of applying a bituminous surface dressing to a concrete foundation (e. g. a road foundation) which is char- :acterized by the employment of a layer of bitu- 120 men-impregnated concrete interposed between the foundation and the surface dressing to act as a bond between them.

In the preferred method, according to the invention, of constructing a concrete road with a 5 bituminous surface, a concrete foundation is first laid in the ordinary way and while the foundation (or at least the upper surface thereof) is :still in a plastic or semi-plastic condition a layer of bitumen-impregnated concrete is applied.

6 Finally, and preferably after the intermediate layer has set, a surface coating of bitumen is applied.

The final coating of bitumen can be applied by the ordinary hot method or by means of an 5 aqueous emulsion of bitumen. The application of bitumen by the medium of an emulsion has the advantage that no heating is required and the emulsion can be laid in practically any weather. Such emulsions are at present used extensively in the surface treatment of macadamized roads and the present invention provides a method by which an emulsion can be employed successfully for the similar treatment of a concrete road. Preferably, in carrying out the invention, the

bitumen-impregnated concrete for the intermediate layer is prepared by incorporating with a plastic concrete mixture, 2, small proportion (say about reckoned by weight on the concrete) of an aqueous bituminous emulsion free from 3 5o soap. Certain aqueous emulsions of bitumen now crete particles to be lacking in uniformity, due

to the fact that the emulsion breaks down and the water becomes separated from the bitumen before adequate coating of the aggregate has oc curred. It is preferable that the emulsion which is mixed with the concrete should be free from soap. Conveniently, the emulsion employed for this purpose is prepared (according to the process described in our copending application Serial lio. 385,070, filed of even date herewith by treating in a colloid mill, in the absence of allrali, a mixture of molten bitumen and an aqueous or acid solution of gelatine or the like.

One example of the construction of a road according to this invention will now be described. In the first place a concrete foundation was laid in the ordinary way and while the latter was still in a plastic condition (i. e. beforeit had set) a layer about half-an-inch in depth, of bitumenimpregnated concrete was applied to the upper surface of the foundation, and trowelled to the approximate contour and then screeded. The bitumen-impregnated concrete was prepared (in a concrete mixer) by incorporating an aqueous emulsion of bitumen with a concrete mixture comprising 4 parts aggregate, 2 parts sand and one part rapid hardening cement, sufficient water being added to bring the mixture to the required consistency for laying. The aqueous emulsion of butumen was prepared by means of a gelatine solution by the process described in our aforesaid application, and the proportion of emulsion introduced into the mixture was about 10% reckoned by weight on the concrete. After the intermediate layer had set, the surface thereof was coated with bitumen by treatment with an 9 aqueous bituminous emulsion prepared by the process described in United States patent specification No. 1,542,626. In another example according to the invention the emulsion was incorporated with a concrete mixture comprising 4 parts aggregate, 2 parts sand and 2 parts cement.

An important advantage of this invention is that the intermediate layer or carpet not only acts as a key between the foundation and the surface coating but also results in producing a finished 111 road with a substantial degree of resilience. The term bitumen as used herein, is intended to be read in a broad sense as including all bituminous and allied material such as bitumen of the type artificially prepared from petroleum, natural lei-C tumens and asphalts, pitch, tar and mixtures of such materials. The term concrete as used herein is intended to define a mixture comprising stone or other mineral aggregate and hydraulic cement. The term bitumen-impregnated concrete is intended to define a concrete as set forth in the preceding sentence with which bitumen has been incorporated. The expression pure bitumen as, used in the claims herein is. not intended to qualify the character or properties of the bitumen but is intended to signify the surface dressing unadmixed with aggregate or the like, in the common acceptation of the term and to distinguish from a bituminous concrete. It will be understood that the process described herein is not limited in application to the construction and repair of roads, but may be applied generally to all concrete structures where one or more of the advantages of a bituminous surface dressing (e. g. its resilience and waterproof properties) is desired.

We claim:

1. A method of surfacing a concrete road with a dressing of pure bitumen which consists first in applying to the road a layer of bitumen-impregnated concrete, and secondly coating said layer with bitumen.

2. A method of constructing a concrete road with a surface dressing of pure bitumen, which consists in laying a concrete foundation and while the latter is still in a plastic condition applying to it a layer of bitumen-impregnated concrete and finally coating said layer with pure bitumen by treatment of the surface with an aqueous emulsion of bitumen.

3. A method of applying a surface dressing of pure bitumen to a concrete foundation which comprises the step of interposing between the foundation and the surface dressing a bondin layer of bitumen-impregnated concrete prepared by incorporating with a plastic concrete mixture a small proportion of an aqueous bituminous emulsion free from soap.

4. A method of applying a surface dressing of pure bitumen to a concrete foundation, which comprises the step of interposing between the foundation and the surface dressing, a bonding layer of bitumen-impregnated concrete prepared by incorporating with a plastic concrete mixture a small proportion of an aqueous bituminous emulsion prepared by treating in a colloid mill, in the absence of alkali,'a mixture of molten bitumen and a solution of gelatin'e. Y

5. Amethod of constructing a concrete road or the like with a surface dressing of pure bitumen, which consists in laying a concrete foundation and while the latteris still in a semi-plastic condition applying to it a layer of bitumen-impregnated concrete prepared by incorporating an aqueous bituminous emulsion free from soap with a plastic concrete mixture in proportions of about l0% reckoned by Weight on the concrete,

and finally after said bitumen impregnated layer has set coating said layer with pure bitumen by treatment of the surface with an aqueous emulsion of. bitumen.

6. The combination of a concrete foundation to which a surface dressing of pure bitumenis keyed by means of an interposed layer of pre-mixed concrete andnormally solidfbitumen.

'7. The combination of a concrete foundation, a layer of pre-mixed concrete and normally solid bitumen superimposed on the foundation, and a thin surface dressing of pure bitumen superimposed on the, intermediate layer and bonded thereby to the foundation.

8. A method of applying a surface dressing of pure bitumen to a concrete, foundation, which comprises in combination the following steps, namely, first preparing a bitumen impregnated concrete by intimately mixing bitumen with concrete, then applying a layer of the'bitumenim pregnated concrete, previously prepared as aforesaid, upon the concrete foundation while the latter is still'plastic, and after said layer of bitumen impregnated concrete has set, applying to, the surface thereof a coating of pure bitumen.

LEONARD 'G N GABRIEL. JOHN FREDERICK BLOTT. 

